The ability to duplicate and store the contents of a storage device an important feature of a storage system. Data may be stored in parallel to safeguard against the failure of a single storage device or medium. Upon a failure of the first storage device or medium, the system may then retrieve a copy of the data contained in a second storage device or medium. The ability to duplicate and store the contents of the storage device also facilitates the creation of a fixed record of contents at the time of duplication. This feature allows users to recover a prior version of inadvertently edited or erased data.
There are space and processing costs associated with copying and storing the contents of a storage device. For example, some storage devices cannot accept input/output (I/O) operations while its contents are being copied. Furthermore, the storage space used to keep the copy cannot be used for other storage needs.
Storage systems and storage software products can provide ways to make point-in-time copies of disk volumes. In some of these products, the copies may be made very quickly, without significantly disturbing applications using the disk volumes. In other products, the copies may be made space efficient by sharing storage instead of copying all the disk volume data.
However, known methodologies for copying data files include limitations. Some of the known disk copy methods do not provide fast copies. Other known disk copy methods solutions are not space-efficient. Still other known disk copy methods provide fast and space-efficient snapshots, but do not do so in a scaleable, distributed, table-driven virtual storage system.
Storage systems also present a need for efficient recovery operations in the event of a failure in the hardware, software, or data associated with a primary data set. Thus, there remains a need for improved copy and failure recovery operations in storage devices.